P4 Flashcards
When do electrons become static?
When they are unable to flow through the medium, if it is an insulator.
What attraction occurs between items with a charge and items without a charge?
Positive attraction
Items with a charge attract to items which don’t have a charge.
What charge do electrons have?
Electrons have a negative charge
What is the attraction between opposition charges?
They attract each other / strong positive attraction
What is the attraction between the same charges?
They repel each other / strong negative attraction
What problems occur with static electricity?
- Attracts Dust
- Damages electronic components
- Cause shocks from door handles
What can be used to prevent sparks and allow static to discharge safely?
Earthing cables
What are the three main uses of static electricity?
- Painting
- Dust precipitators
- Defibrillators
How do paint sprayers work?
The nozzle of the paint gun is charged, causing the paint particles to also become charged. Because each paint molecule gets the same charge they repel away from every other paint particle. This causes the paint to land on the object evenly.
How do dust precipitators work?
In the chimney of a power station the dust particles gain a negative charge. The dust particles then induce a charge on earthed metal plates causing the plates to become negatively charged so the dust attracts to the plates
How do Defibrillators work?
Two paddles with insulated handles are connected to a power supply. These paddles are placed on the patients chest before being charged and then the current is released into the patient, causing the heart to contract
What is radioactive activity?
The number of radioactive particles a substance emits per unit of time.
What is half life?
How long it takes for a radioactive substance to half in mass.
How many particles of carbon 14 are found in living things?
1 part per ten million
What are the three main uses of Ultrasound?
- Ultrasound Scans
- Blood Flow
- Kidney Stone treatment
How is ultrasound used during scans?
Ultrasound is sent into the patient’s body. Some of the ultrasound is reflected at each boundary between different tissues or organs.The depth of each layer is calculated using the time taken for each reflected wave to return. The reflected waves (echoes) are usually processed to produce a picture of the inside of the body on a screen.
How is ultrasound used to measure blood flow?
A probe is placed onto the skin above the blood vessel, it then sends out ultrasound waves and receives them again. A computer can use the pitch of the wave to calculate the rate of blood flow.
How is ultrasound used to treat Kidney stones?
Ultrasound can be used to supply energy to the stone equivalent to its native frequency. This causes the stone to break up.
Why is Ultrasound used for pregnancy scans rather than X-Rays? (2 reasons)
- Ultrasound is not ionizing, it causes less harm to the baby.
- It is also able to image soft tissue much better than X rays can.
What frequency (Hz) does ultrasound start at?
20,000Hz (Above the Human audible range)
What colour is the live wire?
The live wire is brown
What colour is the neutral wire?
The neutral wire is blue
What colour is the ground wire?
The ground wire is green/yellow
What is the cable grip?
The cable grip prevents exposed wires from going out the plug, it is designed to protect the user
What wire does the fuse go on?
The live (brown) wire
What is the purpose of the fuse?
It makes sure too much amperage does not enter the appliance
What happens to the fuse if too many amps are supplied?
The fuse burns out, and needs to be replaced
What is a general rule when replacing a fuse?
That the rating on the fuse should be slightly higher than the rating on the appliance, as it would burn out when the correct amperage is applied.
What is the equation to calculate resistance?
Resistance = Voltage / Current
What is alpha radiation?
Alpha radiation is a helium nucleus.
What is beta radiation?
Beta radiation is a fast moving electron
What is Gamma radiation?
Gamma radiation is a wave
